The present invention refers to a device for automatic cleaning of trashracks at turbine intakes, fresh water intakes, waste water purifying plants and similar, at which a substantially wedge-shaped rake pivotally mounted at the end of a rake arm by driving means is moved together with the rake arm downwards and upwards along the trashrack, said rake arm transferring pulling and pushing forces from the driving means to the rake, the rake arm being mounted to a support, which is displaceable sideways in parallel with the trashrack.
At trashracks trash of different kind, e.g. leaves, water plants and similar, is gathered at which a recurrent cleaning of the trashrack has to be made. In earlier days this cleaning was made manually by means of special rakes, which however was a heavy and physically trying work and besides almost impossible to perform at modern water power plants because of the high trashracks and great water depths occuring there. Therefore automatic raking equipments are nowadays used to a great extent.
In the Swiss patent specification No. 396.779 such a device is described, where a carriage hanging in a lift rope is moved down and up along a trashrack by rolling on the bars of the trashrack. The carriage is provided with teeth extending in between the bars of the trashrack. A bucket is hingedly mounted to the carriage, which bucket during the upward movement of the carriage collects the trash which has been gathered at the trashrack and which during the downward movement is pivoted away from the trashrack. Such a device hanging in ropes is easily effected by side streams, which can occur at trashracks partly blocked up. Besides that no pushing force can be transferred to the carriage during its downward movement. Therefore it would be very difficult to penetrate e.g. an ice layer with this device.
In the Swedish patent specification No. 302.430 is described a raking device comprising a rake member mounted at the end of a rake arm, which can be moved up and down along the trashrack and which is upheld by a support displaceable lengthwise of the trashrack. The rake makes by hydraulic means a cyclic movement, at which the rake arm is lowered to the bottom of the trashrack with the rake at a distance from the trashrack, the rake is then pressed against the trashrack and the rake arm is lifted, at which the rake broughts with the trash gathered at the trashrack and delivers it in a chute or similar above the trashrack. The support is moved sideways and the procedure is repeated until the whole trashrack has been cleaned.
With this device a cleaning of the trashrack is performed only at the upward movement of the rake, at which all trash gathered in front of the trashrack is lifted by the rake and is delivered in e.g. a chute. Especially when the amount of trash is large a lot of power is required for lifting the rake and the device is exerted to considerable stress. A great deal of the trash gathered at the trashrack consists of small soft objects as leaves and plants, which do not cause any damage on e.g. turbines and therefore could be allowed to pass the trashrack.